The invention pertains to the field of sample preparation systems for automated chemical analysis. More, particularly, the invention relates to the field of systems for processing liquid, solid or slurry samples for analysis by liquid chromatography systems.
In many chemical processing plants or laboratories, there is a need for chemical assays for determining the components and/or proportions of the chemical material being dealt with or made. Often this is done using a liquid chromatography system (hereafter liquid chromatography will be referred to as LC). To be suitable for analysis by liquid chromatography, the sample or sample solution must be homogenous, dissolved in an appropriate solvent, and of known concentration (if diluted).
The types of samples which must be dealt with are often quite varied, and often the manner of isolating an aliquot of sample to analyze is quite varied. For example, the sample preparation system may be called upon to prepare samples that are non-homogeneous, two phase, liquid/liquid or liquid/solid samples or slurries with entrained gas bubbles or foam. Further, the sample may be solid in either granulated, powder or tablet form. Some samples may be quite viscous while others are quite thin. Some samples may need to be taken from vats or tanks where they are stored or prepared while other samples may need to be taken from a process stream. Some samples are susceptible to pumping into the sample preparation system while other samples are solid or too viscous to pump and must be physically picked up by an operator of the sample preparation system.
Often it is necessary to dilute samples with solvents before pumping them through an LC column. Very precise control of the sample concentration is necessary in this case. To obtain this precise control, there must be some way to isolate a known volume of sample from the rest of the sample and to release it into a known quantity of diluent.
Prior art sample preparation systems have, to date, not been capable of handling all the above noted situations gracefully. Generally, prior art sample preparation systems are capable of handling only one type of sample, and major modifications or use of an entirely different system is needed to handle a different type of sample.
Thus there has arisen a need for a single sample preparation system which can easily and conveniently handle all the different types of samples which may be necessary to analyze.